Brett Favre's name has frequently appeared on the NFL's weekly injury report over 20 seasons of sprains, strains and painful hits.

This might be the last time: The Minnesota Vikings declared the 41-year-old quarterback doubtful to play Sunday at Detroit because of the lingering effects of a concussion.

Favre wore his red non-contact jersey during Friday's practice, but he didn't have a helmet on and didn't participate in any drills. Vikings interim coach Leslie Frazier declined to address whether or not Favre has passed the post-concussion testing required by the league to return to action.

Favre suffered the head injury during a Dec. 20 game against the Chicago Bears and missed Tuesday night's game at Philadelphia because of it, the second time in three weeks that he sat out after his NFL-record consecutive starts streak ended.

"I'm going to just leave it as doubtful for now, without going into any detail about it," Frazier said. "If we leave him doubtful, it should cover things with him. Never rule him out."